1. Field of the Invention
The present invention relates to a display apparatus and a driving method thereof.
2. Description of the Related Art
Liquid crystal displays (LCD) are one of the most widely used flat panel displays. An LCD typically includes two panels provided with field-generating electrodes such as pixel electrodes and a common electrode, and a liquid crystal (LC) layer interposed therebetween. The LCD displays images by applying voltages to the field-generating electrodes to generate an electric field in the LC layer. The applied electric field determines the orientations of LC molecules in the LC layer to adjust the polarization of incident light.
The LCD comprises a plurality of thin film transistors (TFT) connected with each of the pixel electrodes and a plurality of signal lines connected with the TFTs, such as gate lines and data lines.
Among the LCDs, a vertically aligned (VA) LCD, in which LC molecules are aligned such that the long axes of the LC molecules are perpendicular to the plates in the absence of an electric field, offers a high contrast ratio and a wide reference viewing angle. The reference viewing angle is defined as a viewing angle making the contrast ratio equal to 1:10 or as a limit angle for the inversion in luminance between the grays.
A wide viewing angle of the VA mode LCD can be realized by, for example, cutouts in the field-generating electrodes and protrusions on the field-generating electrodes. The cutouts and the protrusions can determine the tilt directions of the LC molecules. The tilt directions can be distributed in several directions by using the cutouts and the protrusions such that the reference viewing angle can be widened.
However, the cutouts and the protrusions decrease the aperture. Also, the lateral visibility of the VA mode LCD is low. For example, images displayed by a patterned vertically aligned (PVA) LCD equipped with the cutouts become brighter nearer to the lateral sides of the PVA LCD, thereby decreasing lateral visibility.
In order to improve lateral visibility of an LCD, a variety of methods of dividing a pixel electrode into a pair of sub-pixel electrodes, applying voltage to the one sub-pixel electrode using thin film transistor (TFT) and applying voltage to the other sub-pixel electrode using a coupling capacitor so that the sub-pixel electrodes can be supplied with different voltages have been suggested.